Signaling agent realizing method based on media gateway control protocol

ABSTRACT

The present invention discloses a method for realizing signalling agent based on a media gateway control protocol, which comprises the following steps of: providing an agent equipment between media gateways and a media gateway controller that locate in different networks, the agent equipment providing signalling agent and network address translation between different networks; requesting for registering to the media gateway controller from a media gateway; for a MGCP/MEGACO signalling that is not related to media between the media gateway controller and the media gateway, directly replacing a transaction number by the agent equipment and then forwarding; for a MGCP/MEGACO signalling that is related to media, processing a media identifier correspondingly by the agent equipment and then forwarding. According to the present invention, transparent traversing of MGCP/MEGACO protocol among different networks can be realized to make a media gateway controller control media gateways not matter which network they locate in, in which messages on media gateways are dynamically generated by the agent equipment according to MGCP signallings, and operation maintenance cost decreases.

FIELD OF THE INVENTION

The present invention relates to a field of communication technology,specifically relates to a method for realizing signalling agent functionwith a media gateway control protocol.

BACKGROUND

Media Gateway Control Protocol (MGCP), is RFC2705 Protocol of theInternet Engineering Task Force (IETF), and Media Gateway Control(MEGACO) is RFC 3015 Protocol of IETF. Media Gateway Control Protocol(MGCP/MEGACO) is a protocol between soft switch equipment and mediagateway for controlling action of media gateway.

With an idea of discomposing gateways, MEGACO/MGCP protocol discomposesoriginal gateways processing signalling and media stream into two parts:media gateway (MG) and media gateway control (MGC). A physical logicentity on MG can be identified with endpoints, as shown in FIG. 1. A MGCcontrols action of a MG through MEGACO/MGCP Protocol, and processesrequests submitted by a MG; a MG mainly processes information of mediastream. Both MGC and MG are network elements in a network, andcommunicate with each other through MEGACO/MGCP Protocol.

Due to decomposition of MGC and MG, a MGC can control action of multipleMGs, and sometimes such situation may happen that a MGC and MGscontrolled by it locate in different networks and thus an agentequipment is needed to realize signalling agent for MGC's controlling onMGs.

A signalling agent means to realize, by a signalling agent, traversingMGCP/MEGACO signalling and media stream controlled through networks,where MGC and MGs are in different networks and can not be reachable toone another by routes, so as to make MGC enable to control MGs in othernetworks completing call establishing and media streamintercommunicating.

Agent equipment is independent equipment, which provides signalling andmedia stream agent function among networks in a packet switching networkand takes charge of providing signalling and media stream agent betweendifferent networks and network address translation.

At present, a common method for realizing signalling agent amongdifferent networks is based on network address translation (NAT), but inthis method agent equipment cannot make MGC entirely transparent, andcomplexity for realizing call services on MGC is increased; meanwhiledetailed information on corresponding MG needs to be configured on theagent equipment, and, thus, any change on MG under control of MGCrequires informing the agent equipment to change configuration, whichincreases operation maintenance cost.

SUMMARY OF THE INVENTION

In the present invention, a technical problem to be solved is to providea method for realizing signalling agent based on media gateway controlprotocol to overcome shortcomings in the prior art, to implementtransparent traversing of MGCP/MEGACO protocol among different networks,to make MGC not concern network location of MGs, and to decreaseoperation maintenance cost.

The method for realizing signalling agent based on media gateway controlprotocol provided by the present invention comprises the following stepsof:

providing agent equipments among media gateways and a media gatewaycontroller located in different networks, the agent equipment providingsignalling agent and network address translation function amongdifferent networks;

requesting for registering a media gateway in the media gatewaycontroller;

if a MGCP/MEGACO signalling between a media gateway and the mediagateway controller is not related to media, directly replacingtransaction number on the agent equipment and then forwarding; if aMGCP/MEGACO signalling is related to media, processing media attributecorrespondingly by the agent equipment and then forwarding.

All media gateways under same media gateway controller have differentdomain names, every endpoint includes domain name information of themedia gateway, and the media gateway controller can distinguishes mediagateways according to their domain names in endpoint identifiers.

The step of registering media gateways in the media gateway controllerfurther comprises.

sending a register request message from a media gateway to the mediagateway controller, recording message identifier of the media gatewayreceived by the agent equipment to generate a piece of information aboutthis media gateway;

assigning a new transaction number by the agent equipment to theregister request message to replace original transaction number in theregister request message, recording the media gateway sending therequest, and then forwarding the register request message to the mediagateway controller;

sending a register response message to the media gateway from the mediagateway controller after the media gateway registers successfully;

determining the media gateway by the agent equipment according to thenew transaction number in the register response message, replacing thenew transaction number with original transaction number, and forwardingthe register response message to corresponding media gateway.

The step of replacing the transaction number by the agent equipmentfurther comprises:

assigning a new transaction number to each of the request messageregisters sent from the media gateway to the media gateway controller,by the agent equipment, and recording the media gateway sending therequest message;

finding corresponding media gateway by the agent equipment according tothe new transaction number reassigned, after receiving the responsemessage to the request message sent by the media gateway controller,replacing the new transaction number in the response message withoriginal transaction number, and then forwarding the response message tocorresponding media gateway;

sending a request message, sent from the media gateway controller to amedia gateway, to corresponding media gateway by the agent equipmentaccording to domain name in endpoint identifier.

The step of processing a MGCP/MEGACO signalling related to media by theagent equipment further comprises:

creating or modifying corresponding media forwarding port and forwardingtable on the agent equipment after receiving a creating or modifyingconnection signalling sent from the media gateway controller to a mediagateway;

replacing related media information in the signalling with correspondingnetwork address information of the media forwarding port on the agentequipment, and forwarding the signalling to corresponding media gateway;

if the signalling is a signalling for creating a connection, recordingendpoint identifier of the connection on the agent equipment;

modifying forwarding table of corresponding media forwarding port by theagent equipment according to a response signalling when the mediagateway sends the response signalling related to media to the mediagateway controller;

replacing media information in the response signalling on the agentequipment with network address information of corresponding media port,and then sending to the media gateway controller;

sending a release connection signalling to the media gateway from themedia gateway controller after calling finishes, releasing correspondingmedia forwarding port by the agent equipment according to endpointidentifier, and then forwarding the signalling to corresponding mediagateway.

The method of the present invention requires no configuration on anyinformation about media gateways based on MGCP/MEGACO protocol, and themedia gateways can directly be controlled by the media gatewaycontroller. Thus, the media gateway controller does not concern withwhether media gateways are in same network or not, which facilitatesservices realized on the media gateway controller. Meanwhile, any changeon service control on the media gateway needs only perform on the mediagateway controller, but not modify on the agent equipment, thus usermanagement is highly facilitated. Furthermore according to the presentinvention multiple agent equipments may be used for implementing themedia gateway traversing through more networks for multiple times.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a system adopting MGCP/MEGACO protocol;

FIG. 2 is a schematic diagram of an embodiment of a system adoptingMGCP/MEGACO protocol;

FIG. 3 is a flow chart for realizing MGCP/MEGACO information agentaccording to the present invention;

FIG. 4 is a schematic diagram for dynamically generating MG informationon the agent equipment according to the present invention;

FIG. 5 is a flow chart of a registering process from a media gateway toa media gateway controller; and

FIG. 6 is a flow chart of a process for forwarding media stream throughnetworks by signalling agent according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be further described in details in acombination with attached drawings and embodiments below.

FIG. 1 is a schematic diagram of a system in the prior art, which isalready introduced in background and will not repeat here.

In a schematic diagram of a system realizing MGCP/MEGACO signallingagent according to the present invention as shown in FIG. 2, a mediagateway controller MGC and a media gateway MG3 locate in network 1,media gateways MG1 and MG2 locate in network 2, and the media gatewaycontroller controls media gateways MG1, MG2 and MG3 by MGCP/MEGACOprotocol.

According to the method provided by present invention, an agentequipment is provided between MGC and MG1, MG2 that are not in samenetwork, that is an agent equipment between network 1 and network 2. AllMGs under control of same MGC have different domain names, and MGCdistinguishes uniquely each MG by its domain name in endpointidentifier.

The agent equipment has at least two network addresses; one is addressBIP1 in network 1 where MGC locates, the other one is address BIP2 innetwork 2 where MG1 and MG21 locate. IP addresses and port of MGCconfigured on MG1 and MG2 are address BIP2 and port P2 of the agentequipment; and MGC distinguishes MGs by their domain names.

FIG. 3 is a flow chart for realizing MGCP/MEGACO information agent onthe agent equipment according to the present invention, firstly, anagent equipment is provided between MG and MGC in different networks,and provides signalling agent and network address translation functionsamong different networks. Then MG registers to MGC, after registeringsuccessfully, for a MGCP signalling between MGC and MG that is notrelated to media, the agent equipment directly replaces transactionnumber and then forwards; for a MGCP signalling that is related tomedia, the agent equipment processes media identifier correspondinglyand then forwards.

FIG. 4 and FIG. 5 show processes of requesting for registering MG. inMGC;

Step 301: MG sends a RSIP message to MGC for registering, in which itstransaction number is TransID, Agent equipment receives the message onaddress BIP2 and port P2 and records attributes such as source addressand port number of MG message received and domain name of MG, togenerate a piece of information about the MG;

Step 302: The agent equipment reassigns a transaction number TransID′ tothe registering message, replaces original transaction number TransID inthe registering message with it, records corresponding relation ofTransID and TransID′, and then forwards the registering message to MGCfrom BIP1 address;

Step 303: MGC registers MG successfully according to its domain name,and then sends a response message to MG;

Step 304: After receiving the response message returned by MGC fromaddress BIP1, the agent equipment finds corresponding record accordingto the transaction number TransID′ in the response message, obtains MGsending the registering message and its original transaction numberTransID, replaces the transaction number TransID′ in the responsemessage with TransID, and forwards to corresponding MG from addressBIP2.

After receiving each of request messages sent to MGC by MG, the agentequipment reassigns a new transaction number to the request message,replaces original transaction number with the new transaction number,and then records MG sending the request. After receiving a responsemessage returned by MGC for the request message, the agent equipmentfinds corresponding MG according to the reassigned new transactionnumber, replaces the new transaction number in the response message withthe original transaction number, and then forwards the response messageto corresponding MG. For a request message sent to MG by MGC, the agentequipment forwards to corresponding MG according to domain namecontained in the endpoint identifier.

FIG. 6 represents a process for forwarding media stream over networksrealized by MGCP signalling agent through the agent equipment.

Step 401: MGC send MG a signalling CRCX for establishing a connectionport on MG, the agent equipment analyzes the signalling, then knows thatthe signalling is related to media, and establishes a correspondingmedia forwarding port A′ on the agent equipment; if the signalling CRCXhas remote connection attribute, a media forwarding table is establishedon the media forwarding port A′ with IP and port in the signalling, andIP and port in the signalling is modified into address BIP2 and Port A′on the agent equipment; meanwhile, name for endpoint identifier ofconnection to be established by MG is recorded.

Step 402: The agent equipment forwards MG the CRCX signalling withmodified remote connection attribute;

Step 403: after creating the connection port successfully according tothe signalling, MG sends a response message for CRCX signalling, theagent equipment receives the response message, then modifies mediaforwarding table on port A′ with IP and port in local connectionattribute of the response message, and replaces IP and port in localconnection attribute of the response message with address BIP1 and portA′;

Step 404: the agent equipment forwards MGC the response message for CRCXwith modified local connection attribute;

Step 405: MGC sends MG a MDCX signalling for modifying a connection porton MG, and the agent equipment finds media forwarding port A′ accordingto endpoint identifier of MG connection recorded, then modifies mediaforwarding table on port A′ with IP and port in remote connectionattribute of the MDCX signalling, and modifies IP and port in the MDCXsignalling with BIP2 and port A′;

Step 406: the agent equipment forwards MG the MDCX signalling withmodified remote connection attribute;

Step 407: MG returns a response message for modifying connectionsuccessfully;

Step 408: the agent equipment forwards the response message to MGC;

Step 409: after the call ends, MGC sends MG a DLCX signalling forreleasing connection, and the agent equipment finds corresponding mediaforwarding port A′ according to endpoint identifier, and releases mediaforwarding port A′;

Step 410: the agent equipment forwards the DLCX message to MG;

Step 411: MG releases connection according to the signalling, and afterdone successfully replies to MGC; and

Step 412: the agent equipment forwards MGC the reply to the signalling.

If MG needs traverse through multiple networks for multiple times,multiple agent equipments may be used for realization.

It should be noted that the embodiments above are only for describingthe solutions of the present invention but not for limiting. Althoughthe present invention is described with embodiments, an ordinary personskilled in the art should understand that various modifications andvariations may be made in the present invention without departing fromthe spirit or scope of the invention, which all should be covered withinthe scope of the appended claims of the present invention.

1. A method for realizing signaling agent based on a media gatewaycontrol protocol, comprising: providing an agent equipment between mediagateways and a media gateway controller that locate in differentnetworks, the agent equipment providing signaling agent and networkaddress translation between different networks; and requesting toregister the media gateway controller from a media gateway; wherein: fora Media Gateway Control Protocol or Media Gateway Control (MGCP orMEGACO) signaling sent from the media gateway to the media gatewaycontroller, if not related to media, directly replacing a transactionnumber by the agent equipment and then forwarding according to domainname in endpoint identifier; and if the MGCP or MEGACO signaling isrelated to media, processing a media attribute correspondingly by theagent equipment and then forwarding; and if the MGCP or MEGACO signalingis related to media, creating or modifying a corresponding mediaforwarding port and a forwarding table on the agent equipment afterreceiving a signaling for establishing or modifying a connection sent toa media gateway from the media gateway controller, replacing relevantinformation on media in the signaling with information on correspondingnetwork address of the media forwarding port on the agent equipment, andthen forwarding the signaling to the media gateway; and for a MGCP orMEGACO signaling sent from the media gateway controller to mediagateway, sending the request message to corresponding media gateway bythe agent equipment according to domain name in endpoint identifier. 2.The method for realizing signaling agent based on a media gatewaycontrol protocol of claim 1, wherein each of all media gateways undercontrol of same media gateway controller has different domain name, eachendpoint identifier includes domain name information of a media gateway,and the media gateway controller distinguishes media gateways accordingto their domain names in the endpoint identifiers.
 3. The method forrealizing signaling agent based on a media gateway control protocol ofclaim 1, wherein the step of requesting for registering to the mediagateway controller from a media gateway further comprises: sending arequest message for registering to the media gateway controller from themedia gateway, and recording message identifier of the media gatewayreceived by the agent equipment to generate a piece of information aboutthe media gateway; assigning by the agent equipment a new transactionnumber to the request message for registering to replace originaltransaction number in the request message for registering; recording themedia gateway sending the request, and then forwarding the requestmessage for registering to the media gateway controller; registering themedia gateway successfully, and then sending a response message forregistering to the media gateway from the media gateway controller; anddetermining the media gateway by the agent equipment according to thenew transaction number in the response message for registering,replacing the new transaction number with the original transactionnumber, and then forwarding the response message for registering tocorresponding media gateway.
 4. The method for realizing signaling agentbased on a media gateway control protocol of claim 1, wherein the stepof replacing a transaction number by the agent equipment furthercomprises: for each of request messages sent from the media gateway tothe media gateway controller, assigning a new transaction number for arequest message by the agent equipment, and recording the media gatewaysending the request message; after receiving on the agent equipment aresponse message for the request message sent by the media gatewaycontroller, finding a corresponding media gateway according to a newtransaction number assigned, replacing the new transaction number in theresponse message with original transaction number, and then forwardingthe response message to the corresponding media gateway.
 5. The methodfor realizing signaling agent based on a media gateway control protocolof claim 1, wherein the step of processing the MGCP or MEGACO signalingthat is related to media by the agent equipment further comprises: ifthe signaling is a signaling for creating a connection, furtherrecording on the agent equipment an endpoint identifier of theconnection, modifying the forwarding table of a corresponding mediaforwarding port on the agent equipment according to a response signalingwhen the media gateway sends the media gateway controller the responsesignaling related to media; replacing media information in the responsesignaling with information on network address of corresponding mediaport on the agent equipment, and then sending to the media gatewaycontroller; and sending a signaling for releasing the connection to themedia gateway from the media gateway controller after calling finishes,releasing the corresponding media forwarding port on the agent equipmentaccording to the endpoint identifier, and then forwarding the signalingto the media gateway.
 6. The method for realizing signaling agent basedon a media gateway control protocol of claim 2, wherein the step ofrequesting for registering to the media gateway controller from a mediagateway further comprises: sending a request message for registering tothe media gateway controller from the media gateway, and recordingmessage identifier of the media gateway received by the agent equipmentto generate a piece of information about the media gateway; assigning bythe agent equipment a new transaction number to the request message forregistering to replace original transaction number in the requestmessage for registering, recording the media gateway sending therequest, and then forwarding the request message for registering to themedia gateway controller; registering the media gateway successfully,and then sending a response message for registering to the media gatewayfrom the media gateway controller; and determining the media gateway bythe agent equipment according to the new transaction number in theresponse message for registering, replacing the new transaction numberwith the original transaction number, and then forwarding the responsemessage for registering to corresponding media gateway.
 7. The methodfor realizing signaling agent based on a media gateway control protocolof claim 2, wherein the step of replacing a transaction number by theagent equipment further comprises: for each of request messages sentfrom the media gateway to the media gateway controller, assigning a newtransaction number for a request message by the agent equipment, andrecording the media gateway sending the request message; after receivingon the agent equipment a response message for the request message sentby the media gateway controller, finding a corresponding media gatewayaccording to a new transaction number assigned, replacing the newtransaction number in the response message with original transactionnumber, and then forwarding the response message to the correspondingmedia gateway.
 8. The method for realizing signaling agent based on amedia gateway control protocol of claim 2, wherein the step ofprocessing the MGCP or MEGACO signaling that is related to media by theagent equipment further comprises: if the signaling is a signal forcreating a connection, further recording on the agent equipment anendpoint identifier of the connection, modifying the forwarding table ofa corresponding media forwarding port on the agent equipment accordingto a response signaling when the media gateway sends the media gatewaycontroller the response signaling related to media; replacing mediainformation in the response signaling with information on networkaddress of corresponding media port on the agent equipment, and thensending to the media gateway controller; and sending a signaling forreleasing the connection to the media gateway from the media gatewaycontroller after calling finishes, releasing the corresponding mediaforwarding port on the agent equipment according to the endpointidentifier, and then forwarding the signaling to the media gateway.